This invention relates to apparatus and methods for more precisely aligning guide rods and guide pins into bones for bone fixation.
To better understand the problem faced by the inventor and resolved by the invention reference will first be made to the prior art shown in FIGS. 1-4.
Currently available femoral nail systems for the fixation of femoral or certain types of hip fracture and the prophylactic fixation of pending hip or femoral fracture have been described in several trade publications including: (a) The Titanium Femoral Nail System (Synthes); (b) TRIGEN® IM Nail System (Smith+Nephew, Inc.); (c) Intramedullary Hip Screw Nail (Smith+Nephew, Inc.); (d) M/DN® Intramedullary Fixation (Zimmer, Bristol Myers Squibb Co.); (e) AIM® Titanium Femoral Nail System (DePuy ACE, Johnson & Johnson Co); (f) GAMMA Locking Nail (Howmedica); and (g) UNIFLEX Nailing System (BIOMET). These known systems have design features, as shown in FIGS. 1A, 1B, and 1C, which allow insertion of metal rods (e.g., 102), also referred to herein as an intramedullary nail (IM nail), into the medullary canal of the femur (e.g., 104) and insertion of additional lag screws (e.g., 106) or blades (e.g., 108) through slots in the intramedullary nail (IM nail), 102, into the femoral head (110) and neck (112) for additional stability of fracture fixation. FIG. 1A shows the use of two lag screws in the femoral head. FIGS. 1B and 1C show the use of a single blade 108 or screw 106 along the center line of the femoral head and neck. As shown in FIG. 2, known fixation systems include a device commonly called a drill guide, a targeting device, or aiming arm (120) attached to the top end of the IM nail to ensure the correct insertion of lag screws (106) or blades (108) through slots in the IM nail.
Correct positioning of the IM nail 102 is critical to ensure the lag screws or blades are placed in the center of the femoral head 110 and neck 112 in both anteroposterior (AP) and lateral planes for the single screw or blade. For the two screw system as shown in FIG. 1A, the IM nail 102 must also be positioned to cause the two screws to be placed parallel to each other in the AP view and in the center of the femoral head and neck in the lateral view. However, no device or guide is available at this time to aid in the correct placement of lag screws or blades in the center of the femoral head and neck. As shown in the cross-sectional diagram of FIG. 3 (AP view), since the depth of the IM nail 102 is not exactly defined relative to the femoral head and neck, a guide pin 130 driven by means of guide 120 (see FIG. 2) into the femoral head may be too high (position A) or too low (position B), rather than being in the correct center position C. Likewise, as shown in the top (lateral) view of FIG. 4, since the rotation of the IM nail 102 is not exactly defined relative to the femoral head and neck, a guide pin 130 driven via the drill guide 120 into the femoral head may be too anterior (position D), or too posterior (position E), rather than being in the correct center (position F). Thus, in order to obtain correct placement of the guide pin in the center of the femoral head and neck, the surgeon must perform fine-tuning, trial-and-error adjustment by changing the depth and rotation of the IM nail to vary the position at which the guide pin is inserted and repeatedly drilling with the guide pin 130 under fluoroscopic image intensification until a correct guide-pin position is confirmed by anteroposterior (vertical) and lateral (horizontal) views.
This trial-and-error adjustment increases the length of time a patient has to undergo an operation. It also increases the risk of bleeding, wound contamination and subsequent infection. It also increases the likelihood of bone damage from repeated drilling and potential iatrogenic fractures. This also adds unnecessary radiation exposure to the patient, surgeon, and other operating room personnel.
It should also be noted that inadvertent drilling beyond the articular surface of the femoral head is a problem with the presently available systems.
Also, it is frequently difficult to confirm the position of the guide pin in central axis or near the central axis line of the femoral neck and head because the drill guide and its handle hide the true lateral view of the femoral head and neck even where a radio-lucent drill guide is used.
It is an object of the invention to provide apparatus and methods to overcome the problems discussed above.